Molecular evolutionary genetics of crop and weed responses to crowding

Senior Personnel

Resources

Genotypic and phenotypic data generated by this project are available for download here

Abstract

Domestication of wild species is characterized by changes in diverse phenotypic traits,
including inflorescence architecture, fruit and seed morphology, infructescence shattering, and
the timing of developmental events. These changes result from human selection to increase the
harvest index and harvest efficiency. Selection for appropriate environmental responses is also
important in this regard. For instance, higher planting densities could increase yield in many
crop species, but densities are limited by developmental responses to crowding, in which time to
flowering decreases and relative allocation to structural organs increases at the cost of
agronomically desirable traits such as leaf, root, and fruit production. Regardless of the trait
selected in a crop species, agricultural weeds exhibit dramatic and rapid compensatory evolution
that increases weed fitness at the cost of crop productivity. Using comparative genetic and
genomics tools, the proposed research investigates the genetic basis of phenotypic responses to
crowding. The results will contribute significantly to both crop improvement and an
understanding of weed evolution that may aid in management.

The research program focuses on crowding responses in Brassica rapa. In addition to the
morphologically diverse domesticated varieties of B. rapa, naturalized populations occur in both
agricultural fields and disturbed, weedy sites. Thus, this system is appropriate for investigating
both the loci targeted during domestication and those underlying adaptation of weed species to
agricultural settings. Moreover, the near relative, Arabidopsis thaliana, is a model for the genetic
characterization of shade-avoidance responses, facilitating the identification of orthologous loci
under selection in B. rapa. The proposed research takes advantage of current genomic tools to
investigate the genetic basis of competitive responses in agricultural and natural settings.
Specific research goals include 1) identifying quantitative trait loci (QTL) for fitness and traits
affecting competitive ability in field settings in B. rapa and A. thaliana, 2) using controlled light
environments to identify QTL important for response to specific environmental cues, 3)
quantifying evolutionary responses (measured as allele frequency changes) at QTL determining
fitness and phenotypic responses to competition in agricultural and disturbed sites, 4) cloning
QTL for traits important to competitive ability with the aim of determining both genetic targets
for crop improvement and loci underlying evolutionary change in agricultural weeds.